1. Field of the Invention
This invention relates in general to the field of wireless communications, and more particularly to an apparatus and method for providing a multimode smartphone with inter-radio access technology (IRAT) internetworking features and capabilities.
2. Description of the Related Art
The cell phone industry is undergoing exponential growth, not only in this country, but all over the world. In fact, it is well known that the over twenty percent of the adult population in the United States does not have a traditional landline telephone. It is also noteworthy that nearly ninety percent of the adult population owns a wireless phone (i.e. cell phone).
In addition to this growth in ownership, the usage of cell phones is increasing as well over the use of traditional landline telephone coverage. In fact, one in seven adults now uses cell phones exclusively. Whereas in the past cell phones were used when a landline was not available or under emergency conditions, lower carrier rates, affordability of family packages, and free mobile-to-mobile or friend-to-friend promotions have fostered in significant increases in usage. It is not uncommon today to walk into any public forum or facility and observe a majority of the people there talking, texting, or accessing data on their cell phones.
The ability to communicate using a wireless mobile phone has been available since the middle of the last century. However, during the 1990's so-called “2G” or second generation mobile phone systems were fielded that began the growth in both deployment and usage that we currently enjoy today. These initial systems predominately provided for the routing and reliable servicing of voice calls between parties. But even at this time, rudimentary protocols were established to enable cell phones to receive and transmit data as well as voice. Exemplary networks include General Packet Radio Service (GPRS) and Enhanced Data rates for GSM Evolution (EDGE), providing data rates up to roughly 60 Kilobits per second.
During the early 2000's so-called “3G” or third generation cellular systems were fielded that have provided significant increases in user capacity, quality of service, and data rate. CDMA2000, also known as 1xRTT, is perhaps the most prevalent of these 3G systems and this protocol is well known by those in the art to provide for excellent transmission of voice and data. In concert, newer and faster data networks were fielded providing for data rates greater than 2 Megabits per second.
In the past few years, however, there has been an exponential increase in the requirement for data access from a mobile device. Users now check their email, browse the web, and send and receive pictures and movie clips—all from their mobile phones. Accordingly, developers continue to make advances in data networks and protocols to support this pull from the user community. More recently, systems are now being fielded that support so-called Long Term Evolution (LTE) standard, providing for peak data rates up to 100 Megabits per second, as supported by the 3rd Generation Partnership Project (3GPP).
Thus, in addition to supporting legacy data and voice standards, present day cell phone manufacturers must also support LTE. But because of the vast network and modulation differences between LTE and legacy voice and data standards, it has become common practice to develop so-call multimode smartphones that support legacy data standards as well as LTE. To accomplish this objective, smartphone developers typically employ a modem that comprehensively provides for existing voice and data network compatibility, and in addition provide an LTE modem for purposes of accessing the LTE network. More specifically, CDMA modems provide for CDMA-based voice (e.g., 1x RTT) and data (HRPD, EV-DO) communications, but they do not provide for LTE because LTE functions according to an entirely different set of protocols and modulation schemes.
Integrating existing data capabilities with LTE would be less problematic were it not for the fact that LTE is not universally fielded. That is, LTE networks are in their infancy and there are currently only a few pockets of LTE coverage in selected major metropolitan areas. Consequently, cell phone developers must provide for the handoff of data sessions from LTE to legacy data networks and vice versa. And the present inventors have observed that this handoff requirement if extremely onerous from a developer's point of view because the interface requirements of LTE modems are not standardized, thus requiring significant modification of a legacy voice/data modem for each LTE modem in the inventory. Consequently, the development costs—in terms of both investment and time—are substantial when directed at developing a multimode smartphone solution.
Accordingly, what is needed is an apparatus and method that enables existing legacy voice/data modems to be employed in a cellular device in conjunction with an LTE modem from any manufacturer, where interoperation of the two modems is seamless, and where significant modification of the legacy voice/data modem is minimized.
What is also needed is a generalized application programming interface and commensurate hardware that a legacy voice/data modem can utilize to interface and interoperate with a plurality of LTE modems.